1. Field of the Invention
This invention relates to an automatic liquid control system for a clothes washing machine and more specifically to an automatic liquid level control system.
2. Description of the Prior Art
Various methods have been proposed in the past for controlling the amount of liquid added to a clothes washing machine to provide an optimum amount of wash liquid. U.S. Pat. No. 3,065,618 and a corresponding divisional case U.S. Pat. No. 3,093,841 disclose the use of a torque responsive system which senses the torque transmitted from the agitator to the wash tub by means of a mercury sensor switch in combination with a circuit hold relay and a time delay relay to energize the water control system and to introduce an appropriate amount of liquid into the tub for washing purposes. A separate minimum water level switch 90 and a maximum water level switch 92 are provided, agitation beginning and continuing upon operation of the minimum level switch 90. If sufficient water has not been added at the minimum level, torque will be transmitted from the agitator to the basket through the clothes load closing the mercury sensor switch 70 causing additional water to be added to the tub while agitation continues. The time delay relay 100 will cause water to be added for a preselected length of time which is followed by additional sensing of the mercury switch.
U.S. Pat. No. 3,093,841 describes an improvement in the mechanics of the device but the functioning remains the same.
U.S. Pat. No. 3,316,569 discloses a torque responsive pneumatically operated water level control for an automatic washer in which a steel ball is seated on an outlet from an air bleed line, the ball being unseated in response to excessive movement of the tub caused by a transmission of torque from the agitator to the tub. A pressure switch 44 controls the initial fill and once a minimum water level is achieved agitation commences and continues uninterrupted. Excessive movement of the tub causes the air pressure leading to the pressure switch to be reduced thereby resulting in additional filling of the tub with water until the ball remains seated due to minimal tub movement. A separate maximum water level control switch 57 is provided.
U.S. Pat. No. 3,497,884 discloses an automatic water level control for a washer which utilizes a sensor in the drive train of the washer between the motor and the agitator to detect the torque transmitted between the motor and the agitator. Torque sensors such as mechanical or electrical strain gages are used. A minimum water level switch is used to fill the water to a first level and subsequently agitation commences and continues interrupted, additional filling of water being controlled by the torque sensor.
U.S Pat. No. 3,498,090 discloses a torque responsive water level control which senses the relative motion between the tub and the perforate basket mounted within the tub and uses this relative motion as a control for the water valve.
U.S. Pat. No. 4,503,575 discloses an automatic water level control which is responsive to various parameters selected by the user of the washer in which an incoming water volume is continuously measured by a pressure transducer for an initial time period as the clothes are thoroughly wetted. The incoming water volume is continuously measured by the pressure transducer until a minimum level sensor pressure switch associated with the tub closes signaling that a volume of liquid plus clothes load has been received in the washer. This volume is stored in a microprocessor portion of the washer control. The water fill would continue and the volume continuously measured until the total volume of liquid in the washer reaches a precomputed desired volume finding the desired amount of liquid optimum for washing performance for the selected type of clothes load. This volume is determined by computation from the initial minimum level volume, the fabric type and a stored table of optimum values.